1. Field of the Invention
The present invention relates to a control apparatus for an internal-combustion engine, e.g., an in-cylinder direct-injection internal-combustion engine, and more particularly to a high-pressure-fuel-system control apparatus that is provided with a malfunction diagnosis function for realizing, with a simple control method, a diagnosis on whether or not a malfunction is caused in a high-pressure fuel system while the engine is activated.
2. Description of the Related Art
In a in-cylinder direct-injection internal-combustion engine, a so-called high-pressure-fuel-system control apparatus is employed in which a high-pressure fuel is supplied from a high-pressure fuel pump to a fuel injection valve, and the fuel is supplied in such a way as to be injected from the fuel injection valve directly into a combustion chamber.
As a method of diagnosing whether or not a malfunction is caused in such a high-pressure-fuel-system control apparatus, for example, a method disclosed in Japanese Patent Application Laid-Open No. 1998-238392 (Patent Document 1) is known.
In the diagnosis method disclosed in Patent Document 1 described above, firstly, by detecting a fuel-pressure change between the fuel pressure prior to discharge of the fuel from a high-pressure fuel pump and the fuel pressure after the discharge of the fuel, and by presuming a fuel-pressure change between the fuel pressure prior to the discharge of the fuel from the high-pressure fuel pump and the fuel pressure after the discharge of the fuel, based on a drive-timing command value for a flow-rate control valve provided in the high-pressure fuel pump, the difference between the actually measured value and the presumed value of the fuel-pressure change is calculated; in the case where the calculated value exceeds a predetermined determination value, it is determined that a malfunction related to the high-pressure fuel pump has been caused.
However, in general, during the operation of the engine, both the timing of fuel discharge from the high-pressure fuel pump and the timing of fuel injection from the fuel injection valve are changed, based on the operation condition of the engine. When, due to the changes, based on the operation condition of the engine, in the fuel discharge timing and the fuel injection timing, the fuel discharge and the fuel injection are concurrently carried out, the fuel-pressure change due to the fuel discharge cannot be distinguished from the fuel-pressure change due to the fuel injection, with the foregoing conventional determination method, whereby erroneous determination may be made.
Moreover, in general, also upon the activation of the engine, both the control of fuel discharge from the high-pressure fuel pump and the control of fuel injection from the fuel injection valve are started immediately after the completion of discrimination of an engine cylinder; therefore, it is inevitable that the fuel discharge and the fuel injection are concurrently carried out.
When, as described above, the fuel discharge and the fuel injection are concurrently carried out, the fuel pressure is reduced due to the fuel injection, in the case where the fuel-pressure change between the fuel pressure prior to the fuel discharge and the fuel pressure after the fuel discharge is detected, whereby the fuel-pressure change to be detected is diminished; therefore, there is a possibility that an malfunction in the high-pressure fuel pump is determined, even though the fuel discharge is being correctly carried out.
Thus, in Patent Document 1 described above, the fuel-discharge timing and the fuel-injection timing are set in a limiting manner so that, during the operation of the engine, the fuel discharge and the fuel injection are carried out during separate intervals. As a result, the malfunction diagnosis is performed by setting the fuel-discharge timing and the fuel-injection timing in such a way as to avoid the deterioration in the malfunction-determination accuracy.
However, the conventional setting of the fuel-discharge timing and the fuel-injection timing for the purpose of a diagnosis limits the fuel-discharge timing and the fuel-injection timing so as to be deviated from the optimal timings. Accordingly, the pressure of the fuel supplied to the fuel injection valve may not rapidly be raised up to the target pressure corresponding to the operation condition of the engine, or the fuel may not be injected at the optimal timing corresponding to the operation condition of the engine.
[Patent Document 1] Japanese Patent Application Laid-Open No. H10-238392